This invention relates to automotive electrical wiring, power distribution and control systems and more particularly to such a system including semi standardized nodes disposed in strategic vehicle regions and associated with groups of electrical load devices in those regions.
Automotive electrical systems have evolved from the simplest level involving a battery and lights to a more complex level in which the typical passenger vehicle includes a battery, a power distribution center, one or more junction boxes and an extensive array and assortment of accessories including exterior and interior lights, radios, CD players, navigation systems, engine controls, computers, window lifts, ABS, door locks, power mirrors, heating and air-conditioning systems, heated seats, sun roofs, powered sliding doors, power rear deck lifts and other electronic devices.
Among these accessories, hereinafter called xe2x80x9celectrical load devices,xe2x80x9d some are considered xe2x80x9cbasicxe2x80x9d accessories; i.e., accessories which are factory installed on all vehicles in a given vehicle line. These might include radios, engine controls, heaters, some interior lights, exterior lights, wipers and horn. Other accessories such as power window lifts, ABS, heated seats, fog lights, remote entry and air-conditioning may be xe2x80x9cpremiumxe2x80x9d accessories which are routinely installed on premium vehicle lines and are extra cost, special order options on basic lines. Still other accessories are almost always extra cost options. These may include sun roofs, CD players and satellite navigation systems. Wiring harnesses and circuit boards must be individually designed for each accessorization level.
Moreover, it has become desirable to add more sophisticated control features to existing load devices. For example, it is now deemed essential in many vehicle lines to program interior lights to extinguish in a gradual, progressive fashion rather than in the more abrupt fashion associated with common ON/OFF switches. To achieve this type of control as well as to provide for multiple speed settings for such loads as blower motors it has become common to control the application of power to load devices with high-side and low-side switches such as FETs connected to a microcontroller chip which can be programmed to provide the desired input/output transfer characteristic.
To achieve all of the functions in a modem high-level automobile and to provide electrical wiring harnesses and control systems in an economic, repeatable fashion with minimal custom design is a formidable task.
According to the present invention the architecture of an automotive wiring, power distribution and control system is chosen to arrange load devices in groups and control such devices by nodes which are strategically placed in each of several vehicle regions to service the individual groups of load devices. In the preferred form, the nodes are designed in a xe2x80x9ctwo-tierxe2x80x9d fashion to include in each case a first circuit board which is of fixed configuration and which carries a microcontroller and a number of power switches such as FETs at least equal in number to the number of load devices associated with the basic level of accessorization in a specific vehicle region. In addition, each node comprises a second circuit board with terminal connectors to permit it to receive inputs from, for example, a control area network (CAN) as well as power from the vehicle battery and alternator. In addition the boards include splicing of pass through circuits and interconnections between the first and second boards so the CAN signals can reach the microcontrollers to which they are addressed. The interconnections also carry the FET outputs to a terminal connector on the second board so they can be directed to load devices in the region serviced by a given node.
There are numerous advantages arising out of this arrangement. For example, the first circuit board can be standardized and xe2x80x9cqualifiedxe2x80x9d for all vehicles in a line or for vehicles in different lines even though such vehicles may have different levels of accessorization. To this end, the second circuit board is preferably provided with vacant locations for additional power switches such as FETs and additional inputs, which locations are pre-connected by, for exarnple, traces and interconnects to the microcontroller on the first board as well as by traces to an output terminal connector to permit expansion of the accessorization level of any node without affecting the fixed design or load carrying capability of the first circuit board.
In this application, the word xe2x80x9cqualified,xe2x80x9d as it applies to the first circuit board, refers to the determination that the first board provides adequate heat dissipation for the power switching devices, adequate separation of the power devices from the microcontroller and adequate protection of the microcontroller from field effects created by other nearby components.
In a preferred form, the first circuit board is standardized as to size and the FET switches thereon are arranged in a discrete group which is spaced on the board from the microcontroller. Moreover, the second circuit board is provided not only with traces but also with pin-type circuit board interconnects such that the first circuit board can be mounted to and on the second circuit board in parallel spaced relationship to permit air flow between them as well as temperature and field isolation therebetween. The second circuit board is provided with peripheral terminal connectors of standard design secured to the board and electrically connected to traces on the second circuit board by means of L-shaped rigid electrical conductors such that the second circuit board can be connected to receive dc power and control signals on the CAN. The terminal connectors also provide for interconnection of the FET switches to the load devices as well as interfaces to switches and other control interconnections between nodes for networking. As stated above, the second circuit board preferably further includes vacant power switch device locations which are pre-connected by traces to the pin interconnects extending between the second circuit board and the first circuit board such that the vacant power switch device locations, when filled, are pre-connected to the microcontroller. Therefore, to reconfigure a given node for additional load devices requires only the addition of FETs to the second circuit board and flash reprogramming of the microcontroller to put the added FET switches into service. It will be noted that this expansion or xe2x80x9creconfigurationxe2x80x9d does not require redesign of the first circuit board and/or requalification thereof.
These and other advantages of the present invention will be better understood from reading the following detailed description of a specific and illustrative embodiment of the invention.